Star-transit calculator and indicator for mariners



H. L. V. D. GIOT.

STAR TRANSIT CALCULATOR AND INDICATOR FOR MARINERS.

APPLICATION FILED DEC. 1, 1917.

H MISPHERE 1 T I 1 I I I I I 5 i I wwwmm UNITED STATES PATENT OFFICE- HENRI LOUIS VICTOR DESIRE GIOT, or LE HAVRE} FRANCE.

Specification of Letters Patent.

STAR-TRANSIT CALCULATOR AND INDICATOR FOR MARINERS.

Patented July 5, 1921.

Application filed December 1, 1917. SerialNo. 204,822.

To all whom it may concern Be it known that I, HENRI LoUIs VICTOR Diismii G101, a citizen of the Republic of France, and residing at Le Havre, No. 17 Rue G. Cazavan, Seine Infrieure Department, in the Republic of France, have invented certain new and useful Improvements in Star-Transit Calculators and Indicators for Mariners, of which the following is a specification.

This invention relates to mariners planispheres.

Owing to circumstances of time and speed that navigation is now required to satisfy, it is indispensable for mariners to determine as often as possible their position by observation of the stars; the dead reckoning is often a cause of very grave errors which may result in the; worst catastrophies, especially in Waters where there are currents or tides. The sun, particularly in bad weather, very frequently failing and scarcely allowing of taking the latitude except about mid-day, it is necessary to have recourse to the stars.

The object of my invention is to provide an improved planisphere which will allow of facilitating and considerably expediting the observation. by avoiding research groping with regard to points to be observed. This planisphere, all the parts of which are especially combined to minimize the work of the officer of the watch, is arranged for use inboth hemispheres. The declination of thestars is indicated on the planisphere for a given year. The annual variation is also indicated on the planisphere, so that it is possible to calculate the actual declination at any time. 7

. This apparatus allows in a very practical and rapid manner, without calculation, and

without requiring to know the time, of ascertaining the hourlof the passage of the stars at the meridian of any particular place at a given date and, consequently, of taking lat1- tudes as often as the captain may judgenecessary during one night. Consequently it allows of verifying the variation of the com pass at eachpassage of the stars at the me ridian. Y It is, therefore, also from this point of view of great use in the low parts of the northern hemisphere where the polar star is too low on the horizon for determining the latitude. and in the southern hemisphere where the said star is not visible.

In the accompanying drawing,

Figure 1 is a diagrammatic elevation of one face of the'pl'anisphere. For the sake of clearness only a small number of stars are represented and only a portion of each of the graduations.

Fig. 2 is a transverse section of the apparatus. It indicates a plate or frame in which is cut a circular opening. and Z) is a disk which is fitted in this opening in such a manner as to be able to turn freely therein. The adjacent edges of the frame and of the disk are connected by tongue and groove so that these two members cannot be separated when once they have been joined together and are only free to turn with relation to each other.

On the two faces of the disk I) are stuck celestial charts corresponding one with the northern hemisphere and one with the south-i Certain terms, characters and abbreviations used in the following description are defined as follows: AR signifies right ascension.

ARe signifies right ascension of the sun.

ARt signifies right ascension true.

AR-m signifies right ascension mean.

AR* signifies right ascension of a star.

D* or declination signifies zenith distance of a star. r

Ha signifies approximate height.

Midi signifies mid-day. 1

Midi (mid-day) isinscribed in place of O. On the movable disk the largest graduated circumferential line (Z like that of the frame expresses in hours and minutesthe right ascension of the sun. Between two other circumferential lines 0 and f of rather less radii are interposed the months and days of the year, represented by lines spaced so that each ofthem corresponds, on the larger circumference, to the true right ascension of the sun, on the smaller circumference, to the mean right ascension, relatively to the noon (midi) of each day. On each chartare marked the principal constellations of one hemisphere plus those of the other up to 45.

From each of the magnitude extends an arrow 9 which, on the movable frame, corresponds to the right ascension of the said star and indicates upon I the fixed frame, when the instrument is ad justed, the hour of its passage at theupper' meridian of any place, that is the half circle passing through thezenith of that locality. On the arrow h extending from the center to the 21st March can be read the'approxr mate height (Ha) of the star in taking count of the latitude.

The declination of the stars of first and second magnitude is indicated for a given year,- for example, 1874c. The actual declinae tion can-be obtained by means of the annual variation which is indicated beneath the declination.

With regard to the right ascensiondisplacement'of these stars it is represented-by the small lines j placed at the-side and near theend of each arrow 9, the length of each linecorresponding to the displacementjdun ing a given time, for example, 60 years. At thecenter of the planisphere 1S placed a pivot which upon eachside ofithe disk carries a flat metal hand or pointer m. This pointer is slotted through its length and graduated from the polar star (90) to the equator (0) indicated by the dotted circle Q and afterward from 0 to 455. Inthe slot of this pointer the observer caneasily perceive the star observed and determine=or I verify the height thereof (Ha).

At its upper end in the middle of the point ofthe hand is fixed a stud a for rotating it over the movable frame so that any desired star can beconsidered.v

In order to adjust the movable frame it is only necessary to place in coincidence with midi of the fixed frame, the true or mean right ascension of-the sun (ARt or ARm) accordingto whether itis'required-to have the passage of the true or mean time by means of the sun for the given day. a

The upper passage at themeridian ofthe stars observed during the night will then be indicated on the fixedframe bythearrows g which extend from these stars.

7 Therefore, in order to adjust the apparatusitis only necessary to know the date of observed at that time.

the day/and the observerhas. immediately under his eyes,

ARe ARt ARm Ana Dtor declinatiouHa Since at each star, the annual variation and its sign or are read beneath the relative declination at a given year, it is only ne-zessary, in order to find the actual declination, to calculatethe correction by rule of three; for example for Aldebaran D. 16 15' 14.", North +7" 6 1874 to 1 916." We have therefore the .pro-

portion w 7 whence This correction is added to 16 15 714"; I In the case of a planet it is'advlsable to mark its right ascension and its declination;

It is understood that the mean hour of the I passages is obtained like the true hour by usingthe mean AR of the sun or of the date relative thereto instead of its true AB.

The hereinbefore described. apparatus, thereitore,gives very rapidly and very easily and in a precise manner;-

(11) The true hour ofthe' passage of a staratthe meridianr r j I (2) The mean hour of the passage of a star at the meridian.

(.3) The right ascension of a star.

(4) The declination of the stars of .first and second magnitude. By means of the pointer the astral height (Ha) can also be easily determined or verified. To sum, up, all the indispensable elements are easily I obtained 'for calculating the latitude for'calculating the rightascension of a star, for exactly determiningfthepoint, and; for: calculating: the variation of the compass.

The apparatus allows of verifying the. variation ofthecompass at each passageot the stars ,at the meridian. The apparatus, is therefore,.'also from .this point of view, of great interest and importance, in the low parts of the northernhemisphere where the polar star is too low on the horizon for determining the latitude, and in the southern hemisphere where the polar star is not visible. It is understood that in order to determine the latitude ofthe locality, measurements are to be made in the usual way by means of a sextant of the meridian alti tude above the horizon of a;star whose declie nation-is known. I

.Having now particularly described and ascertained the .nature of my said invention the center of the said disk and a revoluble pointer mounted upon the said pivot, the said pointer containing a graduated scale in degrees of altitude counting from the equator, the said plate containing upon the edge of the aperture thereof a circular graduated scale representing a day divided into 24 hours and the subdivisions of the hours, the said disk having represented upon its surface a map of the heavens and near the periphery thereof a graduated time scale of like nature to that of the said plate as Well as two concentric graduated scales representing the year divided into 365 days according to the actual time and the mean time respectively, the same disk also having represented upon the surface thereof the declination of the principal stars at a given period of time as Well as the annual variations of the declinations, substantially as described.

In testimony, that I claim the foregoing as my invention I have signed my name in presence of two subscribing Witnesses.

HENRI LOUIS VICTOR DESIRE (HOT. [13. s.]

Witnesses:

CANs'rAN GNERARE, B. Smnou'r. 

